cito Posted June 9, 2015 Posted June 9, 2015 Hi everyone! My first post ! I hope I'm here right, here's my question: I live in a very dry and hot region of Costa Rica. It rains around 1800mm(around 70,86 in) per year. My property is around 1800 square meters with an elevation of I would say maybe 10 degrees. The house is on the top of the hill. In the dry season, which takes almost up to 6 months, it rains almost never, causing the grass, plants and trees to dry. In the rainy season it can happen that it rains a lot in one day causing some sort of flooding. So I was wandering if I could harvest the rainwater during the rainy season by making some sort of rectangular hole that covers the whole wide at the end of the property which is around 20m. The wide of the hole I was thinking maybe around 2m but what got me thinking was the depth of the hole. I don't know how much water volume i need to keep my property in the dry season green. I would be very much appreciate if anyone could help me deciphering the depth of the hole or has any suggestions regarding this matter. I know there are a lot of other aspects to take care of if I decide to proceed with the construction of the RWH, but I would just like some sort of raw estimation. Best regards, cito
studiot Posted June 9, 2015 Posted June 9, 2015 Rainwater collection and storage is a great idea. Just a few practical thoughts. You are intending to store it for long periods in a hot climate so you will need to think of ways to stop it going rancid or putrid and ways to clean the storage reservoir. Like emptying a swimming pool you would need somewhere to put the water whichilst you did this, or some seasonal cycle to carry the cleaning out. If you dig a hole below the level of your garden you will also have to pump the water back out. I'm sure there are some here with tropical gardens who can tell you better than I can the amount of water you would need to store. You can calculate the available volume by taking the collection area and multiplying this by say 1/4 the average total rainy season rainfall.
fiveworlds Posted June 9, 2015 Posted June 9, 2015 (edited) Grandma had a swimming pool roof built on her house before there was electricity to bring water everywhere in the country. Water would flow into the pool and drain into a water tank in the attic which was then used to flush toilets. She had a well but there was never enough water in the well for anything but drinking water. Edited June 9, 2015 by fiveworlds
Phi for All Posted June 10, 2015 Posted June 10, 2015 Do you have any kind of rainwater retention system now, such as gutters at the edge of your roof leading to downspouts emptying into barrels? If you don't, that might be a much more sustainable first step.
cito Posted June 10, 2015 Author Posted June 10, 2015 Hi studiot thank you for your reply Rainwater collection and storage is a great idea. Just a few practical thoughts. You are intending to store it for long periods in a hot climate so you will need to think of ways to stop it going rancid or putrid and ways to clean the storage reservoir. Like emptying a swimming pool you would need somewhere to put the water whichilst you did this, or some seasonal cycle to carry the cleaning out. If you dig a hole below the level of your garden you will also have to pump the water back out. I'm sure there are some here with tropical gardens who can tell you better than I can the amount of water you would need to store. You can calculate the available volume by taking the collection area and multiplying this by say 1/4 the average total rainy season rainfall. I thought of a way of stop going it rancid or putrid by probably setting some sort of lid or cover that hermetacally seals the hole after the rain stops and a filter should also be set to avoid getting rocks and other kind of solids inside it. It is very important that the hole remains sealed, water stagnation could lead in a Dengue outbreak and that could be pretty bad. How I'm going to set this filter and cover up? I have no idea.. I was thinking probably with some PVC materials or something similar. And you are totally right I will be needing a pump to get the water back out. I'm wondering what kind of pump would work in this scenario, considering that the water is full with sediments and dirt, it would probably break pretty fast. You brought also a very good point regarding the cleaning that's something I guess that will have to occur almost at the end of the dry season. Hi Phi for All Do you have any kind of rainwater retention system now, such as gutters at the edge of your roof leading to downspouts emptying into barrels? If you don't, that might be a much more sustainable first step. I do and that works really good, the grass that is directly to the house remains longer green compared to the rest of the property.
studiot Posted June 10, 2015 Posted June 10, 2015 Looking at rainfall data it seems to depend a bit on where you are in CR. Basing the figures on an average of 18 inches per month for May to December (8 months) you could expect 1/4 x 8 x 18 x 1/36 cubic yards of water per square yard of collection area, which is conveniently 1 cubic yard per square yard, over the season. You would also probably need one of these at the inlet to remove silt that such heavy rainfall would create. https://www.google.co.uk/search?hl=en-GB&source=hp&q=silt+trap+design&gbv=2&oq=silt+trap&gs_l=heirloom-hp.1.1.0l10.1141.2594.0.4563.9.7.0.2.2.0.187.999.0j7.7.0....0...1ac.1.34.heirloom-hp..0.9.1092.cR6nZ0AvKV0
Phi for All Posted June 10, 2015 Posted June 10, 2015 Hi Phi for All I do and that works really good, the grass that is directly to the house remains longer green compared to the rest of the property. But if this water is caught up in barrels, you can redirect it anywhere it's needed on the property. In the US, most houses have at least four downspouts that just dump excess water from the roof onto the ground at the corners of the house. However, I've seen systems in Germany where all the gutters flow into a single downspout, and that leads to a series of catch-barrels, so when one fills up, it overflows into the next. Is this what you have, or is it more like the multiple downspouts we have in the US?
studiot Posted June 10, 2015 Posted June 10, 2015 (edited) But if this water is caught up in barrels, you can redirect it anywhere it's needed on the property. In the US, most houses have at least four downspouts that just dump excess water from the roof onto the ground at the corners of the house. However, I've seen systems in Germany where all the gutters flow into a single downspout, and that leads to a series of catch-barrels, so when one fills up, it overflows into the next. Is this what you have, or is it more like the multiple downspouts we have in the US? This is sometimes called a 'grey water' system where non drinkable water is collected and used for horticulture, toilet flushing or other non drinking uses. It can include recycled household water from the bath, washing machine etc. Edited June 10, 2015 by studiot
Phi for All Posted June 10, 2015 Posted June 10, 2015 This is sometimes called a 'grey water' system where non drinkable water is collected and used for horticulture, toilet flushing or other non drinking uses. It can include recycled household water from the bath, washing machine etc. I hate that most communities in the US classify rainwater as grey. I realize you can't drink it, but I think it has greater utility than using grey water from showers and other non-toilet drains (which I also think should be recycled on my property). My community makes it illegal to retain grey water of any kind. Apparently, our water authority has determined that trapping water decreases revenue they might have made from selling it to us. Honestly, after seeing the systems in Germany, I think just letting rain come off your roof at the corners is very inefficient. We have lots of rainfall now, but it was only a few years ago that we were in drought conditions. My garden would have loved a catch barrel or two. During that time, I used to put a five gallon bucket in the shower with me to catch the excess, and then use that water to flush the toilet the next time I used it. I mentioned the system because cito said the grass near the house was greener than on the rest of the property, and that made me think he had gutters and downspouts, but no catch barrels.
Klaynos Posted June 11, 2015 Posted June 11, 2015 Near a new industrial estate near me they buried square plastic sponges to collect and store rainwater which is then pumped back into properties for use in toilets, watering plants etc... Others I know of use ponds. I imagine investigating the burying approach and seeing how they get the water into systems like that will be better for you given the hot climate. I use a 100l tank from a down pipe off the house, it's not really enough even in the UK summer but most of the rest of the garden that could have another tank is up hill.
Spyman Posted June 11, 2015 Posted June 11, 2015 ...So I was wandering if I could harvest the rainwater during the rainy season by making some sort of rectangular hole that covers the whole wide at the end of the property which is around 20m. The wide of the hole I was thinking maybe around 2m but what got me thinking was the depth of the hole... ...some sort of lid or cover that hermetacally seals the hole after the rain stops... ...How I'm going to set this filter and cover up? I have no idea.. I was thinking probably with some PVC materials or something similar... If you plan to make a big and deep hole then you also need to think about the safety around it. Children or animals can fall down and get hurt and trapped or drown when filled with water.
cito Posted June 12, 2015 Author Posted June 12, 2015 Looking at rainfall data it seems to depend a bit on where you are in CR. Basing the figures on an average of 18 inches per month for May to December (8 months) you could expect 1/4 x 8 x 18 x 1/36 cubic yards of water per square yard of collection area, which is conveniently 1 cubic yard per square yard, over the season. You would also probably need one of these at the inlet to remove silt that such heavy rainfall would create. https://www.google.co.uk/search?hl=en-GB&source=hp&q=silt+trap+design&gbv=2&oq=silt+trap&gs_l=heirloom-hp.1.1.0l10.1141.2594.0.4563.9.7.0.2.2.0.187.999.0j7.7.0....0...1ac.1.34.heirloom-hp..0.9.1092.cR6nZ0AvKV0 I think 18 inches per month would be pushing it a little. According to a study I read here http://www.imn.ac.cr/publicaciones/estudios/Reg_climaCR.pdf the region where I live receives around 1800mm(70.8661 inches) per year, that's 8.83 inches per month in 8 months if I'm not mistaken. One thing I didn't quite understand is how you calculated what I could expect in 8 months. I assume that the 8 and the 18 were for the months in the rainy season and average water per month respectively but the 1/4 and the 1/36 left me thinking. The silt trap is a great idea I would definitely take that in consideration. But if this water is caught up in barrels, you can redirect it anywhere it's needed on the property. In the US, most houses have at least four downspouts that just dump excess water from the roof onto the ground at the corners of the house. However, I've seen systems in Germany where all the gutters flow into a single downspout, and that leads to a series of catch-barrels, so when one fills up, it overflows into the next. Is this what you have, or is it more like the multiple downspouts we have in the US? We have gutters and downspouts that empty in just one barrel but this one never gets full. Near a new industrial estate near me they buried square plastic sponges to collect and store rainwater which is then pumped back into properties for use in toilets, watering plants etc... Others I know of use ponds. I imagine investigating the burying approach and seeing how they get the water into systems like that will be better for you given the hot climate. I use a 100l tank from a down pipe off the house, it's not really enough even in the UK summer but most of the rest of the garden that could have another tank is up hill. Sounds interesting, I've never heard of buried plastic sponges before.
cito Posted June 12, 2015 Author Posted June 12, 2015 If you plan to make a big and deep hole then you also need to think about the safety around it. Children or animals can fall down and get hurt and trapped or drown when filled with water. You are totally right safetly should always come first. I guess I could probably build a fence around it and properly signalize it to avoid this kind of risks.
studiot Posted June 12, 2015 Posted June 12, 2015 1/36 When I went to school there were 36 inches in a yard. 1/4 is an engineering 'collection efficiency factor'. I did state this before, and assumes you can only collect 25% of the rainfall for various reasons. 18 inches per month, well I looked here and waved my guesstimate wand. http://www.costaricaexpeditions.com/AboutCR/tempchart.php
Phi for All Posted June 12, 2015 Posted June 12, 2015 We have gutters and downspouts that empty in just one barrel but this one never gets full. At least you're capturing this much. The system I saw in Germany had 5 barrels, and the 5th one rarely got any water. But that was more than enough to keep the back yard vegetable & herb gardens going, along with some potted flowers. They're either getting a lot more rainfall, or have a much bigger roof.
EdEarl Posted June 12, 2015 Posted June 12, 2015 (edited) If you can terrace your property and spread 4 inches of charcoal, tilled under,it will retain water better than it does now, and you might not need the cistern and pumps. Edited June 12, 2015 by EdEarl
cito Posted June 15, 2015 Author Posted June 15, 2015 1/36 When I went to school there were 36 inches in a yard. 1/4 is an engineering 'collection efficiency factor'. I did state this before, and assumes you can only collect 25% of the rainfall for various reasons. 18 inches per month, well I looked here and waved my guesstimate wand. http://www.costaricaexpeditions.com/AboutCR/tempchart.php You are totally right. Thank you for clearing me out those doubts.
Harold Squared Posted June 16, 2015 Posted June 16, 2015 I have heard of pioneers keeping silver or copper coins in water and even milk barrels, supposedly the ions of metal kept bacterial growth down. Might be something to it since vessels have used copper bottom sheathing to inhibit marine growth.
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